The present invention relates to a multi-coordinate measuring and testing machine which is essentially constituted from a fundamental machine unit, a scanning or sensing system which is movable in at least two coordinate directions, and a machine-controlling unit.
Multi-coordinate measuring and testing machines of that type are counted as being within the general state of technology, and in practical applications, have been introduced a multiplicity of constructions.
2. Discussion of the Prior Art
Current measuring machines, as a rule, are constructed in portal or a gantry-type constructional mode, and are equipped with a mechanical probe or sensor head possessing measuring sensors. Other known measuring and testing machines concern themselves with non-contacting measurement; for example, through the intermediary of interferometer systems. Considered by themselves, both methods of measurement are subject to a series of advantages and also disadvantages.
Thus, for example, known from the disclosure of German Laid-open Patent Application 36 16 812 is a coordinate measuring device with an arrangement for the non-contacting scanning or sensing of the measured object. Through the intermediary of an interferometric linear measurement system, the path of displacement of a measuring mirror for each measuring coordinate, which is fixedly interconnected with the coordinate table. Hereby, the reference mirror of the interferometric linear measurement system is rigidly connected with the scanning system for the measured object such that, with relatively minor technological expenditures, there can also be determined even extremely minute displacements of the imaging objective in comparison with the measured coordinate direction and enabling the preclusion of any influences caused by tilting errors.
The specification of German OS No. 36 16 345 discloses an interferometer system for linear and angular measurement, which is constituted from a total of two interferometer systems, so as to be able to simultaneously implement, at a high degree of precision, linear and angular measurements as well as measurements of refractive index.
The principle of the interferometric linear measurement is already known since the year 1890 from the Michelson Interferometer. However, it is also known that a laser interferometer which is utilized as a linear measurement system, necessitates a not inconsiderable additional expenditures in contrast with other; for instance, mechanical sensor or scanning heads. Through the use of laser interferometer systems there can be achieved a resolution or definition of up to 0.01 .mu.m. However, the length of the laser lightwave is dependent upon the temperature, the pressure and the humidity in the region which is traversed by the measuring beam. Any fluctuation in these environmental conditions will act without inertia or delay on the results of measurement. This signifies that, on the one hand, laser interferometer-linear measurement systems afford an extremely good capability for a precise non-contacting measurement; however, on the other hand, under unfavorable environmental conditions, are capable of delivering erroneous measurement results.
In addition to the above-mentioned non-contacting measuring systems, mechanical sensing or scanning systems are considered to be within the known general state of the technology. These mechanical sensing systems for multi-coordinate measuring machines consist essentially of a spindle on which there is mounted a probe or sensor head, having styli; provided thereon, and sensor balls or spheroids on tips of the styli. The mechanical sensing systems are relatively robust and possess an adequate degree of precision in their measurement. The deflection of the stylus can be either translatory or rotational and, upon contacting the workpiece, generates control signals for the drives. These signals facilitate the provision of constant-remaining, reproduceable or repeatable contacting conditions. In the known sensing systems, a further distinction is made between the measuring and switching systems.
In the measuring sensing systems, in the position of measurement the deflection of the probe stylus is determined through systems for measuring small displacements; whereas in the switching sensor systems, upon reaching of the defined contacting position or a define sensor deflection, a switching signal is generated in the stylus.
Heretofore, prior to the purchase and installation of a coordinate measuring and testing installation, an expert in this technology always needed to extremely carefully investigate the conditions in the utilization and measuring tasks prior to deciding on one or the other installation; namely, either the non-contacting or mechanical sensing system. The provision of both variants of the installations was frequently prohibitive due to space limitations, and integrating as well as cost reasons.